Recently there has been significant focus on the preparation of various polymers from their oligomeric structures. Generally the oligomeric structures have better flow properties than the final polymer and therefore can be used to make various articles where the initial flow is a significant feature of the article. For example, in composite formation the flow of the oligomer is a significant feature in filling the mold and wetting the reinforcing material.
The use of cyclic carbonate oligomers for preparing polycarbonate is a good example of the current focus. By using mixtures of cyclic carbonate oligomers, the softening point of the oligomers is of a sufficiently low temperature that various commercial uses of the cyclic carbonate oligomers are now possible. These uses particularly include the preparation of high molecular weight polycarbonate composite materials. These materials can be used in various applications wherein the general strength and toughness of the polycarbonate is added to by the reinforcing material so that an extremely high modulus is also achieved. The typical method of preparing the polycarbonate composite is to prepare the cyclic carbonate oligomers, add a polymerization catalyst or initiator to the oligomers, add the oligomers to a specific reinforcing material, and raise the temperature to set off the polymerization catalyst or initiator so as to form the high molecular weight polycarbonate resin composite.
This particular method has been found to work well with various fillers such as glass fibers, flakes, aramid fibers and the like. However, with the presence of carbon black together with the cyclic carbonate oligomers, certain problems have occurred in our laboratory. Utilizing a typical catalyst, the predicted linear polymer buildup has not occurred when carbon black has been present with the cyclic carbonate oligomers. Rather, a low intrinsic viscosity has been achieved demonstrating that high molecular weight polycarbonate has not been made. A new catalyst family usually not associated with aromatic polycarbonates has been found to convert cyclic carbonate oligomers to high molecular weight aromatic polycarbonates in the presence of carbon black.